A previously proposed method is known, for example, from the German Published Patent Application No. 195 41 601. In response to a lock-up tendency occurring once at a front wheel, the method described therein provides for increasing the braking force at the rear axle above and beyond the specified driver input. The system pressure, determined with the aid of a sensor, is evaluated as a further criterion for the pressure buildup at the rear axle. The braking force at the rear axle should always be increased in particular when a situation has been recognized, according to which a driver demand for optimal utilization of the transferable braking force is probable. Such a situation is detected when the antilock protection controller has reduced the braking force at at least one front wheel. As soon as the driver releases the brake pedal, the brake pressure in the wheel brakes is reduced according to the driver's command.
German Published Patent Application No. 196 15 805 describes a method for controlling the braking system of a vehicle in open loop, with which, inter-alia, a maximum adhesion is adjusted during one control phase. Starting from a standby phase, there is a change into the control phase when various switch-on conditions are met. For example, the initial pressure adjusted by the driver is evaluated for this purpose. Implemented ABS interventions are not taken into consideration in this connection. As soon as a switch-off condition is met, there is a reversion from the control phase into the standby phase. For example, the initial pressure is evaluated in this connection, as well.
German Patent No. 43 38 065 describes a method for carrying out an automatic braking operation for motor vehicles having an anti-lock system. If the lock-up limit is reached at one wheel of the vehicle, an automatic braking process is carried out. During the automatic braking process, a braking pressure is produced which is greater than the braking pressure resulting from the position of the brake pedal. The braking pressure continues to be increased until, at each axle of the vehicle, the attainment of the lock-up limit for at least one wheel of the axle is determined by the anti-lock system.
German Patent No. 43 25 940 describes a method for determining a threshold value for the actuation speed of the brake pedal. If this threshold value is exceeded, an automatic braking process is triggered, during which a braking pressure is built up which is greater than the braking pressure resulting from the position of the brake pedal. The automatic braking process continuous until a discontinuation criterion is met.
The triggering of the automatic braking process by an ABS-controlled wheel can lead to an instability of the vehicle when the braking pressure at the other wheels is raised into the control range of the ABS. This is particularly the case on roadways having different road-surface coverings. In addition, irregularities in the roadway can lead to false triggerings. In response to the triggering of the support function, the driver can be irritated by the ABS function. The automatic braking process is first broken off with the release of the brake pedal. This means that a quite substantial force hysteresis occurs which holds the brake pedal forward.